1. Field of the Invention
The present invention relates to an apparatus and method of sensing leakage of chemical liquid, and more particularly to an apparatus and method of sensing leakage of chemical liquid, which can sense the leakage of chemical liquid using a flow meter not only in a standby step but also during the proceeding of a process.
2. Description of the Prior Art
Recently, image display devices, such as a liquid crystal display (LCD), a plasma display panel (PDP), and the like, have been rapidly replacing a conventional CRT. Such display devices use a substrate commonly called a flat panel display (FPD).
In order to manufacture a flat panel display, many processes, such as a substrate manufacturing process, a cell manufacturing process, a module manufacturing process, and the like, should be performed. Particularly, in order to form various kinds of patterns on a substrate in the substrate manufacturing process, a photolithography technology is typically used, starting from a cleaning process.
The photolithography technology includes coating photoresist on a layer material formed on the substrate; drying a photoresist solvent in order to volatilize the photoresist solvent; performing a soft baking of the photoresist at a relatively low temperature; putting a photomask on the photoresist and then exposing the photoresist layer in accordance with a pattern formed on the photomask; developing the exposed photoresist layer; performing a hard baking of the developed photoresist at a relatively high temperature; and patterning the layer material exposed through the photoresist layer.
On the other hand, in many processes including the photoresist coating process, various kinds of chemical liquids are dispensed onto the substrate using a slit nozzle and so on. Accordingly, it is very important to sense and prevent leakage of chemical liquids which may occur in a valve or a pipe when the chemical liquids are dispensed.
Conventionally, in order to sense the leakage of chemical liquid, a capacitance type sensor has been used. The capacitance type sensor is a non-contact type sensor which uses a change of capacitance between an object to be detected and the ground, and outputs a detection signal when an object to be detected approaches a detection surface of the sensor. If an object to be detected approaches, the capacitance of the sensor is increased as the polarization thereof is increased due to static induction, while if the object becomes apart from the detection surface of the sensor, the capacitance of the sensor is decreased as the polarization thereof is decreased. The capacitance type sensor senses the existence/nonexistence of the object by detecting the amount of change of the capacitance. Specifically, the capacitance type sensor detects the object in a manner that if the object approaches the sensor, the capacitance of the sensor is increased to cause the vibration breadth of an output voltage of the sensor also to be increased, and an output unit of the sensor is operated through amplification of the vibration breadth of the voltage to detect the object. By using the capacitance type sensor, not only the position detection and fixed-position stop control of the object can be performed but also the existence/nonexistence and level of the liquid can be detected.
Conventionally, in order to sense the leakage of the chemical liquid, a flow meter has also been used. The amount of leakage of the chemical liquid is measured using the flow meter, and if the measured amount of leakage exceeds a predetermined value, the leakage state of the chemical liquid is reported to a user.
However, the conventional apparatus for sensing the leakage of the chemical liquid has the following problems.
In the case of sensing the leakage of the chemical liquid using the capacitance type sensor, a small amount of leakage of the chemical liquid cannot be sensed. In particular, the leakage of the chemical liquid occurring on a back side of the substrate cannot be sensed. Accordingly, in order to sense such a small amount of leakage of the chemical liquid, a separate sensor should be installed.
Also, in the case of sensing the leakage of the chemical liquid using the flow meter, the leakage can be detected only in a standby step before the whole process is performed. Accordingly, during the proceeding of the process or in a state that dispensing of the chemical liquid is interrupted, the leakage of the chemical liquid cannot be sensed.